The invention generally pertains to automated die-punching machines. More specifically, the invention relates to a removable die assembly that provides access to individual die pins of an automated die-punching machine.
Automatic die-punching machines with die pins are often used to punch regular, repeating patterns of holes through stacks of paper sheets in preparation for binding. Typically, such a machine receives a stack of sheets and actuates to advance die pins toward the stack to punch the appropriate holes through each sheet in the stack substantially simultaneously. The pins are then reset to punch holes in another stack. Printing or document reproduction businesses often handle particular binding jobs consisting of a large number of thick stacks. As a result, a principal advantage of automatic die-punching machines is their capacity to efficiently perform a uniform, repetitive, high speed punching operation, potentially requiring a high punching force, on a collection of stacks that is fed into the machine.
Although automatic die-punching machines offer improvements over manual punching processes, regular die maintenance or changing the machine""s punching parameters for particular punching jobs can be a time-consuming process requiring disassembly of the machine. For example, the size or arrangement of holes, and the number of sheets per stack vary widely between punching jobs, requiring particular configurations of die pins. Further, the service life of die pins varies inversely with frequency of their use. As a result, frequent modification of the punching parameters or regular die pin maintenance requires stopping the machine for disassembly, thus decreasing efficiency of the machine.
Mitigation of these difficulties has been attempted. For example, U.S. Pat. No. 6,047,623 (xe2x80x9cthe ""623 patentxe2x80x9d) to Whiteman, et al, describes an xe2x80x9cimproved die assembly and mounting means, allowing the die assembly to be quickly installed and removed without bolts, screws, or housing panel removal.xe2x80x9d According to the disclosure, xe2x80x9cthe die assembly need not be bolted to the machine frame . . . and may be quickly removed simply by being unclamped . . . and slid out of the machine housing.xe2x80x9d This construction of such devices allows quick and easy maintenance and changeover of the die pins, although it is subject to a number of particular shortcomings.
In the ""623 patent, the die pins are positioned in holes with the pin heads disposed in an elongated recess in a pin retainer plate. A relatively thin pin strap positioned over the pin heads is pivotally connected to a bolt at one end. A slot at the other end of pin strap releasably engages a bolt to keep pin strap in contact with the pin heads. The ""623 patent die assembly employs a C-shaped stop member secured to the die to prevent disengagement of the pin retainer, pins, and pin strap from the die. Since the pin strap is rotatably attached to a bolt at one end, and slidably engages another bolt at a second end, the pin strap disclosed in the ""623 patent is retained in position only by friction. The resulting disadvantage is that the pin strap can slip off inadvertently during removal, disassembly, maintenance, or storage of the die assembly, thus allowing the pins to become disengaged. The commercial embodiment of the ""623 patent die assembly further includes a hook extending in a perpendicular plane at the end of the slot. The hook extends over the edge of the pin retainer plate in an attempt to prevent the strap slot from becoming disengaged.
In a similar design by a German manufacturer, Renz, the pin retainer strap is secured to the pin retainer plate by bolts extending through openings in either end of the strap. To access the pins, one or both of the bolts are removed.
It is a primary object of this invention to provide a device that facilitates quick and easy removal and replacement of a die assembly with die pins in an automated die-punching machine.
It is a further object of this invention to provide a die assembly that secures die pins within a die assembly and prevents their inadvertent release or separation from the assembly.
Another object of the invention is to provide a die assembly that reduces the number of components needed to prevent inadvertent exit or removal of the die pins from the die and eliminates the need for extraneous tools.
The present invention is thus directed to a particular die pin retaining arrangement in a die assembly for use with a die punching machine for punching holes in paper stacks, wherein the die assembly facilitates quick and easy removal and replacement of the die assembly and individual die pins therein.
The invention provides a die assembly that easily slides into and out of a die punching machine, permitting an operator to install or remove it without tools. The die assembly includes a frame member, a die subassembly, die pins, and a die pin retainer subassembly. The frame member typically extends longitudinally along the length of the die assembly. A handle is affixed to the frame member to facilitate user handling of the die assembly. The handle extends outside of the die punching machine when the die assembly is installed and affords a person a designated gripping area for removing, installing, and handling the die assembly.
The die subassembly of any appropriate design is also coupled to the frame member. The die subassembly includes two substantially parallel die plates separated by a shim, thus forming a slot or die throat. Inasmuch as the stack of papers to be punched is inserted between the plates, the width of the shim determines the size of the paper stack that is receivable by the die assembly. When the stack is to be punched, the die pins are forced to slide through holes in one of the plates of the die subassembly until they impinge on the stack. The pins are further driven through the stack and through holes in the other plate of the die subassembly, thus punching holes in the stack. After the holes are punched, the pins are forced back out of the paper stack by springs or other biasing mechanism and the process is repeated on the next stack.
To transmit the punching force to the pins and to facilitate their quick and easy maintenance, the pins are retained in the die pin retainer subassembly, which is forced toward the die typically by the ram of a punching machine. The subassembly includes a die pin retainer which has holes that slidably receive the pins such that the retainer is disposed between the pin head and the die. The subassembly also includes a retaining bar, which is disposed over the pin heads to maintain the pins in the retainer. The retaining bar typically receives the punching force from the ram or punch driver in the punching machine. Since it covers and contacts each of the pin heads, the retaining bar provides for the even distribution of the punching force simultaneously to each of the pins along the length of the bar.
The retainer is preferably affixed to the frame member by one or more locking bolts or the like. In the preferred embodiment, each of the bolts has a substantially smooth shaft that allows the retainer to slide toward the die as the pins are driven into the die. Springs are disposed along the bolts between the retainer and the die to constantly bias the retainer away from the die so that one or more sheets may be received in the die throat for punching. Since the holes in the retainer are smaller in diameter than the die pin heads, the spring force that biases the retainer from the die also causes the die pins to disengage from a previously punched stack. The locking bolt heads physically stop the retainer from disengaging the bolts as a result of the spring force. Accordingly, the bolt lengths are tailored such that the bolt heads limit the retainer before the pins emerge completely from the die, eliminating the need for a separate stop member.
According to an important feature of the invention, the die pin retainer and the retaining plate of the retainer subassembly nest or engage one another to prevent relative lateral movement. Preferably, both are generally channel-shaped. In operation, the downwardly extending legs of the retaining bar are preferably disposed inboard the upwardly extending legs of the channel-shaped retainer to secure the retaining bar over the die pin heads and virtually prevent any relative lateral movement of the retaining bar within the channel-shaped retainer. In this way, the retaining bar extends along the length of the channel-shaped retainer, covering the tops of the pin heads, thus preventing them from sliding out of the channel-shaped retainer.
In order to further releasably lock the retaining bar so as to minimize relative vertical and longitudinal movement between the retainer and the retaining bar, the components include engaging structures that may be engaged to minimize relative movement, or disengaged to allow the locking bar to be moved from its position covering the pin heads. In the preferred embodiment of the invention, the ends of the retaining bar include protrusions that may be disposed subjacent a segment of the head of the locking bolt. In this way, while the nesting of the channel structures of the retainer and the retaining bar prevent lateral relative movement of the retaining bar and the retainer, the locking protrusions further minimize longitudinal and vertical movement when engaged. The protrusions may also include one or more tabs that act as handling structures to facilitate locking and unlocking of the retaining bar.
The design of the die assembly of the present invention is thus an improvement over the prior art. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.